1. Field of the Invention
This invention relates to muffled structures for the firing of ceramic ware. In some types of firing operation it is essential that the ware should be protected from the direct action of the heat source of a kiln in which it is fired, since this would damage the ware.
2. Description of the Prior Art
Muffled kilns have been known for some time but have disadvantages, especially lack of versatility. For example, it is not usually possible to deal with a batch of ware, only some of which needs protecting from the heat source.
When tunnel kilns are used, mobile kiln cars are loaded with ware and passed through the kiln. It has been proposed to muffle the kiln car superstructure by the use of ceramic baffles which enclose some or all of the shelves thereof and which form upright walls secured in place relative to the superstructure.
The superstructure generally includes spaced upright pillars and, in one prior proposal, clips are provided on or adjacent the top and bottom of the pillars and, at a central position between adjacent pillars, a lower clip only is provided level with the bottom of the pillars. It will be appreciated that the pillars support shelves which carry the ware and the lowest rows of pillars are supported on the base of the kiln car, these supporting the lowest shelves and then further pillars are disposed above, resting upon the lowest shelves and so on until the structure has the requisite size.
The baffles used are ceramic plates which can be fitted at the pillars to the upper and lower clips and which are of sizes such that there is sufficient "play" to enable them to be only loosely connected at the pillar clips. This enables the plates to be rocked or "hinged" somewhat at the pillar clips. In general, two plates meet at each central clip which is in the form of a grooved ceramic block, arranged for pivotal movement about a position in which it is aligned with the plates in their aligned, "in use" condition, to catch and release the baffle plates.
Because of the amount of play necessary in the sizing and fitting together of the parts, great problems occur if the space between vertically adjacent shelves is relatively great and the baffles are tall. The baffle plates, being held only loosely, tend to wobble as the kiln car is moved through the kiln and the plates can fall out causing damage to the kiln car superstructure, the ware carried thereon and possibly blockage of or damage to the tunnel kiln.
It is possible to use ceramic pins or pegs passing through portions of the kiln car superstructure such as the shelves into the edges of the baffle plates to hold them securely in place but this arrangement involves the use of extra skilled labour to insert the pins and increases the costs because the pins (being of ceramic material) tend to be brittle and to break. Furthermore, the openings needed to receive the pins tend to weaken the parts in which they are provided and the pins can fall out and mark the ware.